An egg is an "egg-celant" idea, birdmama! (Sorry, I couldn't resist!) If he/she is truly a crow, you're better off because healthy crows will eat just about anything. They are constantly on the look-out around here for goodies. Baked goods, meats, pet food, along with their wild diet of bugs and stuff. They also will eat carrion, like vultures. But I don't know about an injured or ill crow.
Whatever you're going to do about it, don't fuss with the bird too much. Human contact without proper medical and nutritional attention would most likely stress the bird. Settle it down for the night with food and water in as safe a place as you can, then leave it alone. If it's still going strong in the morning, then you've got another problem: what to do with it then!